Mobile aerial platform

ABSTRACT

The platform includes an upstanding support structure carried by a wheeled vehicle. A boom is pivotally connected at one end to the upper end of the support structure. A platform is pivotally carried by the boom at its opposite end. At least one fluid cylinder connects between the support structure and the boom to raise and lower the boom and platform. A pair of flexible lines are fixed at opposite ends to the support structure sides and the platform, respectively and are reaved over sheaves on the boom whereby the platform is partially supported thereby and maintained in a horizontal position throughout the full range of pivotal movement of the boom. The platform is mounted on a vehicle, for example, a truck, trailer, fork-lift truck, and the like.

United States Patent 1191 Spillman MOBILE AERIAL PLATFORM [76] Inventor: Robert L. Spillman, 221 S. Cassady Ave., Columbus, Ohio 43209 [22] Filed: July 7, 1972 [21] Appl. No.: 269,811

[s2] U.S. C1. 182/2, 182/63 [51] 1111.01 18661 11/04 [58] Fieldof Search 182/2, 63, 141; 280/150 G [56] References Cited UNITED STATES PATENTS 489,628 1/1893 Colleret 280/150 G 1,975,119 10/1934 Oates 280/1500 2,969,849 1/1961 Grant 182/2 3,016,973 H1962 Williamson 182/148 3,078,949 2/1963 Hoard 182/2 3,196,979 7/1965 Garnett 182/2 3,283,850 11/1966 Jones 182/2 3,415,339 12/1968 Range 182/2 1111 3,826,334 July 30, 1974 Primary ExaminerR einaldo P. Machado Attorney, Agent, or Firm-LeB1anc & Shur [5 7] ABSTRACT The platform includes an upstanding support structure carriedby a wheeled vehicle. A boom is pivotally connected at one end to the upper end of the support on a vehicle, for example, a truck, trailer, fork-lift truck,-and the like.

14-Claims, 8 Drawing Figures PAIENIEBJIMOIQH 3.826.334

sneer 1% 3 PAIENTEDaaemn I a.aas'.3a4

} sum BM 3 MOBILE AERIAL PLATFORM The present invention relates to a vehicle mounted elevatable platform and particularly relates to a platform for lifting workmen and/or materials to work areas elevated above ground level.

Devices for lifting men and materials, vehicle mounted or otherwise, are well known. Many such devices, however, are heavy, complicated in construction, expensive and due to their sheer size and bulk do not permit in most instances, use of a vehicle such as a truck for its intended purpose, i.e., for carryingmaterials etc. That is to say, while many of these lifting devices are mounted on light vehicles, i.e., pickup-type trucks, the lifting devices per se occupy a substantial part of the space in the truck and preclude its use for carrying substantially anything other than the lifting device itself. Furthermore, many of the prior art elevatable platforms require the use of outrigger assemblies for stabilizing the platform particularly when it is elevated to its maximum height. While Outriggers are effective to stabilize the platform, they have the disadvantage of preventing movement of the vehicle on which the elevatable platform is mounted. In other words, it is necessary to disengage the outriggers prior to moving the vehicle and this normally entails lowering the platform before the vehicle is moved to another position. Still further,.many prior devices of this type utilize complicated linkages and power-assisted assemblies for maintaining the platform level throughout its range of elevation, all of which add to the size and cost of the vehicle.

Moreover, prior lifts of this type are normally designed for a specific installation, i.e., in a specified type and size of truck. These designs are not readily adapted to other types of vehicles nor provide for any interchangeability of parts.

The present invention provides an elevatable platform adapted for mounting on a vehicle which minimizes and/or eliminates the above-noted and other disadvantages of prior vehicle-mounted platforms and provides a novel and improved vehicle-mounted elevatable platform having various advantages in construction, mode of operation,'and use in comparison with such prior platforms. Particularly, the present invention provides an upstanding. support structure comprised principallyof a pair of upstanding generally triangular frames spaced laterally one from the other and adapted at its base for securement to a vehicle. In one embodiment of this invention, the frames are secured to the bed of a pickup truck. In another embodiment, the frames are secured to a base having channel-shaped elements for receiving the tines of a fork-lift .whereby the platform is mountable on a fork-lift truck. The upper ends of the support structure pivotally mount one end of a boom which pivotally carries a platform at its opposite end. One or more cylinders are pivotally coupled between the support structure and the boom whereby the platform can be selectively raised and lowered.

Further, the platform is pivotally carried by the boom about an axis offset rearwardly of the center of gravity of the platform. To maintain the platform level at each elevation, the present invention provides a pair of cables connected at one end to the support structure and at their opposite end to the lower forward edge of the pivoted'platform and forwardly of the center of gravity of the platform. The cables are reaved over sheaves carried by the movable boom. Coil springs connect between boom extensions and the rear ends of the platform on the rearward side of its pivotal axis. The platform is thus tensioned between the spring and the cables at each elevation of the platform whereby it .is maintained substantially level at each elevation thereof. Moreover, the cables are located at predetermined positions along the boom, support structureyand platform as to remain substantially constant in length as the platform is raised and lowered. The foregoing arrangement of the cables, springs and offset pivotal mounting for the platform also reduces the moment about the cylinders and permits use of smaller cylinders than would otherwise be the case.

It is a feature of the present invention that the platform hereof, when mounted on a pickup-type truck,

occupies such minimum space that over 90 percent of the normal usable space in this type of truck remains available for carrying materials, tools and the liker To accomplish this, the fluid pumps and associated equipmentare mounted at the front of the vehicle bed, Also, the platform per se, in this embodiment hereof, is formed of a substantially open frame. Moreover, the support frames are mounted along opposite sides of the truck. Accordingly, when the platform lies in its lowermost position adjacent the end of the truck overlying the open tailgate, the bed of the pickup truck is readily accessible through the open platform and remains substantially free for the storage of materials and the like as desired.

It is a further feature hereof that the vehicle on which the platform is mounted in one embodiment hereof carries a device for bypassing the suspension of the vehicle whereby the support structure is rigidly mounted on the vehicle wheels for stabilization while simultaneously the vehicle is permitted to be moved if desired. Particularly, the vehicle is provided with a pair of rods threaded to the vehicle frame. The rods carry a support at their lower ends for engagement with the rear axle of the vehicle. Under normal conditions of road travel,

' the support is spaced from the axle. When it is desired to bypass the vehicle suspension, the rods are threaded downwardly such that the support bears against the axle and raises the vehicle frame sufficiently to support the platform directly from the axle. Thus, swaying of the platform due to the vehicle suspension is entirely eliminated. Also, the vehicle is free for travel on its wheels with the platform elevated whereby the location of the platform relative to a work area can be changed in a minimal time and safety.

It is a still further feature that'an embodiment of the present invention permits the elevatable platform to be mounted on a fork-lift truck'whereby the combined elevating capacity of the platform and fork-lift are achieved. To this end, the support frames mounted on 1 3v Accordingly, it is a primary object of the present invention to provide a novel and improved vehiclemounted aerial platform.

It is another object of the present invention to provide a'vehicle-mounted aerial platform wherein the platform and its supporting structure and elevating devices are designed to minimize the space-occupied thereby and to maximize the usable space available in the truck with the platform carried thereby for carrying materials,'tools and the like.

It is stilllanotherobject of the present invention to provide-a vehicle-mounted aerial platform wherein the platform deck is maintained in a substantially horizon-v tal positionthroughout its full range of movement by a pair of cables connected at predetermined locations along the platform support structure and which cables Referring now to the drawings, particularly to FIG. 1, there is illustrated an aerial platform generally designated and mounted on a truck T. Platform lllcomprises a base support structure generally indicated 12 carrying a boom generally indicated 14, the end of 1 which pivotally. carries a platform 16. Base structure 12, as best illustrated in FIG. 2, includes a pair of laterally spaced side frames each including an upstanding also support a part of the load carried by the platform. I

form including adevice for bypassing the'suspension of the truck and thereby supporting the platform directly from the axle of the truck and eliminating instabilities caused by the truck suspension.

It is a related object of the invention to provide a mobile platform having the foregoing characteristics whichtis electrically insulated from ground.

It is a still further object of the present'invention to provide a novel and improved vehicle-mounted aerial platform which is selectively mountable on a fork-lift truck whereby increased elevations are obtainable, together with valuable horizontal reach possibilities.

. It is a related object of the present invention to provide a novel and improved vehicle-mounted aerial platform which is simple and inexpensive in construction, light in weight, reliable in service, safe, requires no setup time, and. utilizes electrical systems conventionally provided the vehicles on which the platform is mounted or systems which maybe self-contained as desired.

These and further objects and advantages of the present invention will become more apparent upon refer-' ence to the following specification, appended claims and drawings wherein: I

FIG. 1 is aperspective view of an aerial platform constructed inaccordance with the present invention and mounted on a pickup-type truck;

FIG. 2 is an enlarged cross sectional view of the aerial platform and portions of the truck illustrated in FIG. 1 with the platform illustrated in elevated and lowered positions.

FIG. 3 is a cross sectional view thereof taken generally about on line 3-3 in FIG. 2; H I

I FIG. 4 is a' fragmentary enlarged perspective view of the tip of the boom illustrating the pivotal mounting for the platform;

FIG; Sis a side-elevational view of an aerial platform constructed in accordance with the present invention and mounted on a trailer; 1

FIG. 6 is a side elevational view of an aerial platform constructed in accordance with the present invention specifically adapted for use with a fork-lift-type truck;

I conjunction with a fork-lift truck.

support 18 and an upwardly inclined support 20, supports 18 and 20 being suitably secured at their lower ends to the truck bed 22; Thus, the support 20 in each side frame forms the hypotenuse of a generally right triangle which, in the embodiment illustrated in FIGS. 1-4, includes, as one of its lower legs, the truck bed 22. Each support 20 is suitably secured to the upper end of the corresponding support 18 and extends forwardly thereof terminating in a hub 24 for pivotally mounting thev boom 14 described hereinafter. Support structure 12 includes a support 26 between upright supports '18 as well as-crossed tensioned rods 28. For reasons hereinafter noted, the area between the triangular side frames is open and without cross-bracing, the upper end of supports 20 being provided a cross support 30. Supports 18 and 20 as well as various of the other support structure described herein may comprise I-beams.

Boom 14 comprises a pair of laterally spaced support arms 32 pivotally coupled at their forward ends about pins 25 received in hubs 24 on supports 20 and also in hubs 37 formed on the ends of arms 32. Support arms 32 are suitably cross-braced at spaced locations by transverse braces 34 and crossed tensioned rods 35. Boom 14 is thus a substantial rigid integral structure. Along the topof each arm 32 there is provided a truss rod 38 spaced above arm 32 by a torsion rod brace 40. A turnbuckle 42 is also provided each rod 38 whereby the rods are maintained under tension providing additional strength to the boom 14. The distal ends of support arms 32 terminate in hubs 42 for receiving pins 44 also carried by the platform 16 whereby platform 16 is pivotally carried at the tip of boom 14. I V

Platform 16 is comprised of a lower deck 46 having upstanding sides including front and rear uprights 48 and 50, respectively, a longitudinally extending memher-52 connecting the upper ends of uprights 48 and 50, a pair of closely spaced uprights 54 spaced closer to rear upright 50 that to front upright 48, and a cross brace 56. The sides, are, in turn, secured one to the other by transversely extending front and rear braces 58 and 60, respectively, secured at the upper ends of front and rear uprights 48and 50. For reasons previously noted, the platform is substantially open in a front to rear direction between the sides thereof without any cross-bracing except transverse braces 58 and 60. Ad-

jacent the upper end of each pair of intermediate uprights 54, there is provided a support bracket 63 for carrying the pin 44 received in hubs 42 on arms 32, pins 44being suitably secured in place as desired. As noted from the drawings, the pivotal axis of platform 16 islocated rearwardly of its center of gravity'and this is advantageous, as set forth hereinafter, in the system. for maintaining the platform level at each elevation thereof and in reducing the moment about the cylinder whereby cylinders of less capacity may be utilized-- To pivot boom 14 relative to support structure 12, there is provided on each side thereof a fluid actuated cylinder 65 pivotally coupled at one end as at 56 to support bracket 67 mounted on upstanding support 18. The piston rod 68 of cylinder 65 is pivotally connected at its distal end to a bracket 69 mounted on the underside of support arm 32. It will be appreciated that extension and retraction of thepiston rods 68 relative to the cylinders 65 displaces boom 14 upwardly or downwardly, respectively, carrying platform 16 therewith. Note that the pistons and cylinders are located on the outside of the side support frame thus leaving the space between the support frames unencumbered.

The motor, pump and fluid reservoir for operating the cylinders 65 are indicated 94 and are located toward the front end of truck bed 22 between upright supports 18. The pumps are connected through suitable fluid lines, not shown, to the cylinders and it will be appreciated that the cylinders are operated in a conventional manner. Also, the controls for raising and lowering the platform are preferably located on platform 16 as indicated at 96. 7

To maintain the platform deck 46 level throughout the full range of elevation of platform 16, the truss rod 38 on each arm 32 is extended beyond the hub 42 and shaped to provide a hook 70. One end of a coil spring 72 is received over the hook and its opposite end is coupled to the rear upright 60. In the lowermost position of the platform and hence least extended condition of the springs 72, platform 16 is biased by springs 72 for movement about hubs 40 in a counterclockwise direction as illustrated in FIG. 2. To preclude the pivotal movement of platform 16 and to maintain platform deck 46 substantially level at all elevations thereof, there is provided on each side of the device a cable 74 connected at one end to the-lowerand rearmost part of platform 16, i.e., connected along the rear edge of deck 46 on one side thereof. Each cable 74 is reaved over a pulley 76-carriedon support arm 32 and is connected at its opposite end to an eyelet 77 on support 20. A spring 78 forms a part of the cables and servesto absorb various shock loadings imposed on the platform during use.

Accordingly, with the foregoing described structure, it will be seen that the platform 16 is tensioned between the springs 72 and cables 74. That is, with the platform in the lowermost postion, the springs 72 are chosen such that a light force tending to rotate the platform 16 about its pivotal axis is provided, i.e., 100 lbs. This force is counteracted by a like force tensioning cables 74. It has been discovered that, by locating the cable connections at predetermined locations along the base structure, boom and platform, a constant length of each cable may be provided for maintaining the platform substantially level for each elevation thereof. For example, as the'platform is raised, each cable portion between pulley 76 and eyelet 77 increases in length in an amount corresponding to the decrease inlength of the cable portion between pulley 76 and the lower rear edge of platform 16. The locations of the cables along the base structure, boom and platform are thus critical and may be found by applying the following equation;

I, 1 1w [r s 2rs/ V2 (cos 0 sin (1)1" V. 2 [l --c0s (0--0i)]" where l, and I, the lengths of cables 74 respectively between eyelet 77 and pulley 76 and between pulley 77 and lower forward edge of platform 16 'at the highest elevation of the platform, the sum of which remains a constant;

w the distance between the form and pulley 76;

r the ratio of the distance between the pivotal axis of the boom and the point of connection of the cables to the support structure to the distance between the point of connection of the cables to theboom and the pivotal connection between the boom and platform;

s the ratio of the distancebetween the pivotal connection of the boom and the support structure and the pulley 76 to the distance between the pointof connection of the cables to the boom and the pivotal connection between the boom and platform;

, 6 the angle the boom makes with the horizontal at an elevated position thereof a the included angle formed by a line extending from the pivotal connection of the platform and boom to the point of connection of the cable with the platform and the horizontal. 1

Accordingly, from the above, it will be appreciated that a proper choice of r and s maintains the change in l, l /w to less than one-tenth radians. illustrated choice of such ratios is r 0.95 and s 1.6.

Furthennore, it will be appreciated from a review of pivotal axis of. the plat- FIG. 2 that-the force exerted by the springs tending to' rotate platform 16 in a counterclockwise direction increases as the platform increases in elevation. This increasing force is, of course, counteracted by increasing tension in cables 74. The tensioned cables 74 thus carry part of the loadings imposed on the boom by the weight of the platform 16 and the men and materials carried thereby. The load transferred to the cable acts on the boom at a location closer to the connection between the boom and piston rods 68 than the pivotal axis of the platform relative to the boom thereby reducing the moment about the piston rods. This, in turn, permits a reduction in the capacity'of the cylinders utilized than would otherwise be the case.

It will be appreciated that the raising of workmen,

tools and/or material at various elevations above truck T, for example, to the height illustrated by the dashed lines at FIG. 2, may cause the truck and platform 14 to sway in a lateral direction or become generally unstable. This instability is, in part, due to the flexibility of the suspensionsystem normally employed by a truck of this type, i.e., leaf suspension springs. To eliminate this instability, there is provided in accordance with the present invention a devicefor directlysupporting the truck and platform carried thereby from the wheel axles whereby the weight of the truck platform is transferred from the suspension system to the axle and hence directly to the ground through the truck wheels.

To this end, there is illustrated at 80 in FIGS. 2 and 3 a wheel axle and a device generally indicated 82 for transferring the truck and platform weight directly to the axle bypassing the truck suspension system. The device 82 includes on each side of the truck a bracket 84 which mounts a pair of internally threaded supports 86 which receive a vertically extending screw rod 88. The top of rod 88 mounts a handle 90 while its lower end carries a pad 92 for hearing on axle 80. Upon rotation of rod 88, the pad 92 is raised or lowered into and out of engagement with axle 80. Thus, during normal use of the truck, that is, when the truck is en route to a worksite, screw rods 88 are threaded such that pads 92 are spaced well-above the wheel axle 80 whereby the truck is conventionally carried on its suspension. Upon arrival-at the worksite, rods 88 are threaded to engage pads 92 against axle 88 thereby limitedly lifting the truck and transferring its weight and the weight of the platform from the suspension system directly to the axis and wheels. Note that this transfer does not inhibit movement of the truck and it is a significant feature hereof that the truck can be moved while stabilized in the manner set forth. This is particularly significant where only a few feet of movement isrequired as it obviates any necessity to lower the platform in order to move the platform very short distances.

In utilizing the aerial platform hereof, the truck, of course, is driven to the job site with the pads 92 spaced from axle 80.- It willbe noted from a review of FIG. 3 thatthetruckbed 22 is substantially open when the platform is in its lowermost position resting on the rear end of bed 22 and the lowered tailgate 98. Since the area between the platform is substantially unencumbered and since the support structure 12 for theplatform hereof is locatedadjacent opposite sides of truck bed 22, the bed per se is available for carrying materials, tools, and the like with very little, if any, interference from the platform. ,At the job site, the screw threaded rods 88 are threaded in brackets 86 whereby pads 92 are lowered to engage axle 80 and the weight of the truck and platform is transferred directly to the axle bypassing'the conventional truck suspension. The workmen may then step onto the platform deck 46 andlor'load it with tools, materials and the like. By manipulating controls-96 pistons68 are extended from cylinders 65 whereby boom 14 is pivoted about hubs 24 to the desired elevation. The controls, of course, may be located at the base of the platform if desired. It will be noted that throughout this elevation, the platform deck is maintained substantially horizontal by means of the constantlength wires 74 andsprings 72 irrespective of platform elevation. As will be appreciated from a review of FIG. 2, a shiftingof the weight of the workmen and/or materials on the platform to the rearmost edge of deck 46 is counterbalanced by springs 72. In any shift of weight or workmen, materials, tools, or the like toward-the front of the platform, platform deck 46 is restrained from pivoting into a non-horizontal position by theconstantlength wires 74. A snoted previously,

the truck can be advanced or moved backwards when the platform is elevated and without transferring the weight of the truck, platform and men and/or materials carried thereby back onto the truck suspension system. That is, the truck can bemoved forwardly or backwards while pads 92 engage axle 80. Obviously, for those jobs located at minimum elevation, the suspension bypass system 82 need not be utilized. Like parts in. the following embodiments of the present invention illustrated in FIGS. 5, 6-7 and 8 are respectively designated with like numerals as in the prior embodiment hereof illustrated in FIGS. l-4 with the letters a succeeding the reference, numerals.

' Referring .now to the embodiment hereof illustrated in FIG. 5, an aerial platform constructed in accordance with the present invention is mounted on a trailer rather than atruck. Boom 14a and platform 16a are identical in all respects as previously described in the previous embodiment. In this form, however, the lower ends of supports 20a and upright supports 18a are connected directly to a trailer frame designated 100.

Referring now to the embodiment hereof illustrated in FIGS. 6-7,- there is disclosed an aerial platform generally designated b specifically adapted for use in conjunction with a forklift truck whereby the elevations achieved by the platform and fork-lift truck separately are combined. to obtain significantly greater heights than when utilized separately. To accomplish this, boom 14b, raising and lowering mechanism 65b, platform 16b, are identical in all respects to the respective boom 14, platform 16, and mechanism 65 disclosed in the first described embodiment. The support base 12b, however, is comprised of a pair of channelshaped members 110 spaced laterally one from the other. Channels 110 are in turn mounted on front and rear channels 112 and 1 14 whereby channels 110, 112,

and 114 form a substantially rectangular frame. The

' lower ends of legs 20b are secured to the rear ends of channels 110 while the lower ends of upright supports 18b are secured at the forward ends of channels 110. The power package 94b for operating the platform may be carried on forward channel 114 and a suitable cross brace 116.

It will be appreciated that with the foregoing de- I The fork-lift is of conventional construction and the tines are carried by a carriage 120 supported for vertical movement on a pair of upstanding guides 122. In use, the platform 106 can be stored in any out-of-theway position. When it is desired to utilize the greater height capacity of the combined fork-lift and platform arrangement hereof, the fork-lift F is driven to the location of the platform and the tines 118 inserted into the slots of the base structure. The fork-lift F is then moved to the work area and the carriage 120 and the entirety of the platform 10b carried thereby are elevated along guides 122 ina conventional manner. Platform 16b is then also elevated by actuation of cylinders 65b. Thus, in this manner, the height capacity of a conventional fork-lift truck is advantageously augmented without diminution of its normal capabilities since the platform can be readily mounted on and demounted from the tines of the fork-lift. Y

Referring now to FIG. 8, there is illustrated a further form of platform 10c specifically adapted for use with a fork-lift truck in a manner similar to the embodiment illustrated in FIGS. 6 and 7. In this form, the boom, platform and raising and lowering mechanism for the boom are substantially the same as described with respect to the previous embodiments and therefore are not specifically described or illustrated. However, the

base structure 12c is modified to provide a more compact unit. To thisv end; base structure includesla substantially rectangular base 126 comprised of longitudinally extending side members 128 interconnected at their front and rear ends by channels or braces 130. Side members 128 have inwardly directed flanges 132 which define with braces longitudinally extending laterally spaced slots 134 for receiving the tines of the fork-lift truck. The members 128 are short as compared with members 110 in the previous. embodiment. Also, upstanding'support 20c is supported at its lower end in spaced relation from base structure 126 by a pair of uprights 136. Suitable cross-bracing is provided between members 128 as indicatedat 138 and also between the uprights 180 as indicated at 140. Thus, the foreshortening of the base in this embodiment provides a very compact unit occupying a minimum amountof space when not in use.

The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. .The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

What is claimed and desired to be secured by United States Letters Patent is:

1. An aerial platform for mounting on a vehicle comprising an upstanding support structure, a boom pivotally carried at one end by said support structure, a platform pivotally carried by said boom adjacent its opposite end and having a deck for carrying a load, means carried by said support structure and coupled to said boom for pivoting the latter thereby to raise and lower said platform relative to said support structure, and means coupled between said support structure, said boom and said platform for maintaining said deck in a substantially horizontal position throughout the range of pivotal movement of said boom relative to said support structure, said coupling means including a' flexible line connected at one end to said base structure and extending therefrom continuously for connection at its opposite end to said platform, a sheave carried by said boom, an intermediate portion of said line being reeved about said sheave, whereby the portion of the line between the sheave and said platform decreases in length and the portion of the line between the sheave and said base structure-increases in length in response to pivotal movement of said boom in a direction to raise said platform.

2. A platform according to claim 1 wherein said line carries a part of the load carried by said aerial platform, said line remaining substantially constant in overall length throughout the full range of pivotal movement of said boom.

3. A platform according to claim 1 wherein said platform ispivotally connected to said boom adjacent the upper end of said platform, said platform deck forming a leg of a right triangle with the other leg extending from said upper pivotal connection to said platform deck and the hypotenuse extending from the pivotal connection to the connection of said line to said platform.

4. A platform according to claim 1 wherein said pivoting means includes at least one fluid-actuated cylinder having opposite ends pivotally coupled to said base structure and said boom.

5. A platform according to claim 1 wherein said platform is pivotally connected to said boom adjacent the upper end of said platform, said latter pivotal connection lying on one side of the center of gravity of said platform, said line being connected to said platform on the other side of said gravity whereby said line carries a part of the load carried by said platform, said line reing the platform for movement about'its pivotal connection with said boom in a direction to make said line taut.

7. A platform according to'claim I mounted on a vehicle having a body, means for securing said support structure to said vehicle body, a suspension for said vehicle, wheels carried by said suspension, and means carried by said vehicle for selectively bypassing said suspension and rigidly coupling said support structure to said wheels.

8. A platform according to claim 7 wherein said wheels are carried by an axle, said suspension including aspring between said support structure and axle, said bypassing means including a support rod movable between a first position spaced from said axle and a second position engageable with said axle, said vehicle being movable on said wheels when said rod lies in either of said positions.

9. A platform according to claim 1 wherein'said support structure has a base, said base having a pair of laterally spaced generally longitudinally extending slots for receiving the tines of a fork-lift.

10. A platform according to claim 9 wherein said base comprises a pair of inverted channel-shaped members, cross bracing between said inverted members, and means spanning the underside of said channelshaped members for retaining said base on the tines.

11. A platform according to claim 1 wherein said support structure includes a pair of laterally spaced frames, said boom including a pair of framing elements respectively pivotally connected at one end to said frames, cross bracing between said elements, said platform being pivotally connected to the opposite end of said elements and lying therebetween, said pivoting means including a fluid actuated cylinder pivotally coupled between the frame and boom element on opposite sides of the platform, said coupling means between said boom and said base structure including a pair of flexible lines respectively connecting at one end said frame and extending continuously for connection at their opposite ends to said platform on opposite-sides thereof, a sheave carried by each of said elements, intermediate portions of said lines being reeved about said sheaves respectively whereby the portion of the line between said sheave and said platform on each of the opposite sides thereof decreases in length and the portion of the line between said sheaves and said frame on each of the opposite sides of said platform increases in length in response to pivotal movement of said elements in a direction to raise the platform.

12. A platform according to claim 11 wherein the ends of said elements extend beyond-the pivotal connectionbetween said elements and said platform,

maining substantially constant in overall length throughout the full range of pivotal movement of said boom.

6. A platform according to claim 5 including a spring connecting between said boom and said platform biassprings connecting between saidelement and said platform biasing said platform for pivotal movement in one direction, said lines being connected to said platform at a location whereby said lines are tensioned by said springs.

13. A platform according to claim 12 wherein said lines carry a part ,of the load carried by said platform, said lines remaining substantially constant in overall length throughout the full range of pivotal movement of said boom. v

14. A platform according to claim 13 mounted on a vehicle having a bed defined by upstanding sidewalls, said support structure being mounted adjacent the forward end of said truck with said platform in its lowermost 'position'overlying said bed at the'open rear end of the truck,'said platform being defined by upstanding side supports and a deck extending between the lower ends of said side supports and a substantially open framework whereby access to said bed is available through the open framework of said platform.

050 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3, Dated July 1974 In e Robert L. Spillman It is certified that error appears in the above-identified -patent: and that said Letters Patent are hereby corrected as shown .below:

In Col. 7, line 46, ""A snoted" shouldr'ead f-As noted-- In Col. 8, line 31, "platfgrm 1.06." should read platform 10b;.

IS Signed and sealed this 3rd day of December 1974.

(SEAL) Attest:

McCOY M. GIBSON JR; Attesting Officer c. MARSHALL DANN Commissioner of Patents 

1. An aerial platform for mounting on a vehicle comprising an upstanding support structure, a boom pivotally carried at one end by said support structure, a platform pivotally carried by said boom adjacent its opposite end and having a deck for carrying a load, means carried by said support structure and coupled to said boom for pivoting the latter thereby to raise and lower said platform relative to said support structure, and means coupled between said support structure, said boom and said platform for maintaining said deck in a substantially horizontal position throughout the range of pivotal movement of said boom relative to said support structure, said coupling means including a flexible line connected at one end to said base structure and extending therefrom continuously for connection at its opposite end to said platform, a sheave carried by said boom, an intermediate portion of said line being reeved about said sheave, whereby the portion of the line between the sheave and said platform decreases in length and the portion of the line between the sheave and said base structure increases in length in response to pivotal movement of said boom in a direction to raise said platform.
 2. A platform according to claim 1 wherein said line carries a part of the load carried by said aerial platform, said line remaining substantially constant in overall length throughout the full range of pivotal movement of said boom.
 3. A platform according to claim 1 wherein said platform is pivotally connected to said boom adjacent the upper end of said platform, said platform deck forming a leg of a right triangle with the other leg extending from said upper pivotal connection to said platform deck and the hypotenuse extending from the pivotal connection to the connection of said line to said platform.
 4. A platform according to claim 1 wherein said pivoting means includes at least one fluid-actuated cYlinder having opposite ends pivotally coupled to said base structure and said boom.
 5. A platform according to claim 1 wherein said platform is pivotally connected to said boom adjacent the upper end of said platform, said latter pivotal connection lying on one side of the center of gravity of said platform, said line being connected to said platform on the other side of said gravity whereby said line carries a part of the load carried by said platform, said line remaining substantially constant in overall length throughout the full range of pivotal movement of said boom.
 6. A platform according to claim 5 including a spring connecting between said boom and said platform biasing the platform for movement about its pivotal connection with said boom in a direction to make said line taut.
 7. A platform according to claim 1 mounted on a vehicle having a body, means for securing said support structure to said vehicle body, a suspension for said vehicle, wheels carried by said suspension, and means carried by said vehicle for selectively bypassing said suspension and rigidly coupling said support structure to said wheels.
 8. A platform according to claim 7 wherein said wheels are carried by an axle, said suspension including a spring between said support structure and axle, said bypassing means including a support rod movable between a first position spaced from said axle and a second position engageable with said axle, said vehicle being movable on said wheels when said rod lies in either of said positions.
 9. A platform according to claim 1 wherein said support structure has a base, said base having a pair of laterally spaced generally longitudinally extending slots for receiving the tines of a fork-lift.
 10. A platform according to claim 9 wherein said base comprises a pair of inverted channel-shaped members, cross bracing between said inverted members, and means spanning the underside of said channel-shaped members for retaining said base on the tines.
 11. A platform according to claim 1 wherein said support structure includes a pair of laterally spaced frames, said boom including a pair of framing elements respectively pivotally connected at one end to said frames, cross bracing between said elements, said platform being pivotally connected to the opposite end of said elements and lying therebetween, said pivoting means including a fluid actuated cylinder pivotally coupled between the frame and boom element on opposite sides of the platform, said coupling means between said boom and said base structure including a pair of flexible lines respectively connecting at one end said frame and extending continuously for connection at their opposite ends to said platform on opposite sides thereof, a sheave carried by each of said elements, intermediate portions of said lines being reeved about said sheaves respectively whereby the portion of the line between said sheave and said platform on each of the opposite sides thereof decreases in length and the portion of the line between said sheaves and said frame on each of the opposite sides of said platform increases in length in response to pivotal movement of said elements in a direction to raise the platform.
 12. A platform according to claim 11 wherein the ends of said elements extend beyond the pivotal connection between said elements and said platform, springs connecting between said element and said platform biasing said platform for pivotal movement in one direction, said lines being connected to said platform at a location whereby said lines are tensioned by said springs.
 13. A platform according to claim 12 wherein said lines carry a part of the load carried by said platform, said lines remaining substantially constant in overall length throughout the full range of pivotal movement of said boom.
 14. A platform according to claim 13 mounted on a vehicle having a bed defined by upstanding side walls, said support structure being mounted adjacent the forward end of said truck with said platform in its lowermost position overlying said bed at the open rear end of the truck, said platform being defined by upstanding side supports and a deck extending between the lower ends of said side supports and a substantially open framework whereby access to said bed is available through the open framework of said platform. 